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142
Background
Pediatric hemophagocytic syndrome (HS) is a
distinct clinical entity in which excessive
uncontrolled activation and proliferation of Tcells
and macrophages occur and are often fatal. First
described in 1939 by Scott and Robb-Smith as a
histiocytic reticulosis, a neoplastic proliferation of
histiocytes,
1
this syndrome has since then been
given several other denominations, including
hemophagocytic histiocytosis, histiocytic disorder,
macrophage activation syndrome, and reactive
hemophagocytic lymphohistiocytosis (HLH).
2,3
To date, this syndrome remains ill-recognized in
children, leading to false or delayed diagnosis
and suboptimal management. Etiologically, HS is
a component of several inherited disorders in
which it is present at onset or during the course of
the disease. It has also been associated with a
variety of viral, bacterial, fungal, and parasitic
infections, as well as with collagen-vascular
diseases
4–6
and malignancies, particularly T-cell
malignancies.
7
The association between HS and
infection is important because both sporadic and

familial cases of HS are often precipitated by
acute infections; HS mimics overwhelming
infectious sepsis, misleading diagnosis,
8
and may
obscure the diagnosis of precipitating treatable
infectious illnesses, including visceral
leishmaniasis and tuberculosis.
9–12
The diversity of
diseases associated with HS and its strong link with
intracellular infections have led to delays in
determining etiology and initiating proper care. In
recent years, our knowledge of the common
pathogenic mechanisms underlying this disorder
has dramatically improved, and the terminology
Review
Pediatric Hemophagocytic Syndromes:
A Diagnostic and Therapeutic Challenge
Nada Jabado, MD, PhD; Christine McCusker, MD;
Genevieve de Saint Basile, MD, PhD
Abstract
Pediatric hemophagocytic syndrome (HS) is a severe and often fatal clinical disorder. This syndrome is
frequently unrecognized, and thus, affected children may receive suboptimal management, leading to
an increase in mortality. The purpose of this review is to provide a clinical guide to (1) the recognition of
HS based on clinical, biologic, and pathologic features; (2) the identification of the primary cause of HS
in a given affected child; and (3) the initiation of effective treatment in a timely manner.
N. Jabado — Division of Haematology and Oncology,
Department of Paediatrics, Montreal Children’s Hospital,
McGill University Health Centre, Montreal, Quebec;

C. McCusker — Division of Allergy and Immunology,
Department of Paediatrics, Montreal Children’s Hospital,
McGill University Health Centre, Montreal, Quebec;
G. de Saint Basile — INSERM U429, Hôpital Necker
Enfants-Malades, 149 rue de Sèvres, 75015 Paris, France
Correspondence to: Dr. Nada Jabado, Division of
Haematology and Oncology, Department of Paediatrics,
Montreal Children’s Hospital, McGill University Health
Centre, Montreal, PQ H3Z 2Z3; E-mail:

N. Jabado and C. McCusker are recipients of a “Chercheur
Boursier” Award from Fondation de la Recherche en Sante
au Québec
Pediatric Hemophagocytic Syndromes — Jabado et al 143
and classification of disorders associated with HS
are under revision. This review aims to provide
clinicians with
1. a definition of HS as a clinical and biologic
entity that will help with the recognition of this
syndrome in an affected child and the initia-
tion of proper management;
2. a classification of potential diseases leading to
HS, based on our current knowledge of their
molecular defects and providing the current
means of establishing a molecular diagnosis;
and
3. a brief overview of available treatment
options, based on our understanding of disease
mechanisms.
Recognizing HS

Etiopathogenesis
In response to infection, innate and adaptive ele-
ments of the immune system act in concert to clear
the pathogen and generate memory cells of adap-
tive immunity.
13,14
In a physiologic (normal) sit-
uation, triggering of the immune system by an
intracellular organism leads to transient activation
and expansion of the lymphohistiocytic com-
partment. Transient production of interferon-␥
(INF-␥) leads to transient expansion and activa-
tion of both the lymphocyte and macrophage
compartments. The intensity of the immune
response depends on the type of infecting antigen,
its structure, dose, localization, and duration of
infection in the host.
15
Once the initial infection
has been cleared, control of the response in nor-
mal individuals results in contraction of the
immune system and a return to baseline for both
lymphoid and macrophage lineages, with gener-
ation of a few memory T and B cells (Figure
1A). Homeostasis of the immune system is
impaired in diseases that lead to HS. Whether
the underlying primary defect is in the lympho-
cyte or in the macrophage compartment, uncon-
trolled expansion and activation of mostly
CD8

+
lymphocytes and macrophages occur, lead-
ing to an unending positive feedback loop on
both cell lineages. T cells continuously produce
INF-␥ and tumour necrosis factor-␣ (TNF-␣),
which in turn continuously activate and induce the
proliferation of Tcells and activate macrophages.
Activated macrophages expand and infiltrate the
reticuloendothelial tissues (including bone mar-
row, liver, spleen, and lymph nodes, which can
result in organomegaly)
3
and the perivascular
structures of the brain, inducing central nervous
system (CNS) involvement.
16–18
These activated
macrophages avidly phagocytose all nearby
hematopoietic lineages, including red blood cells
(hence the term “hemophagocytosis”), granulo-
cytes, and platelets (see Figure 1B). They produce
cytokines, including interleukin (IL)-1, TNF-␣,
and IL-6.
19
High levels and prolonged production
of these cytokines result in fever, hemodilution
with hyponatremia, hypertriglyceridemia, and
coagulation abnormalities. Also, oversecretion
of IL-18 by monocytes in patients with HS has
been described

20
and may further enhance TNF-
␣ and IFN-␥ production by T lymphocytes and
natural killer (NK) cells as well as induce Fas lig-
and expression on lymphocytes, enhancing their
cytotoxic effect. Increased serum levels of solu-
ble Fas ligand, which can trigger apoptosis in
such Fas-expressing tissues as the kidney, liver,
and heart, are also seen in HS and may result in
organ failure through increased apoptosis of cells
in these tissues.
21
In summary, HS results from the failure of
down-regulating and limiting a T helper 1
(Th1)–type immune response after it is triggered.
This may occur, as detailed below, through intrin-
sic cytotoxic T-cell and NK-cell dysfunction in
patients such as is seen in hereditary forms or in
rheumatoid arthritis, impairing the host ability to
control underlying infectious triggers; or, alter-
nately, it may occur through ongoing stimulation
of a Th1 immune response that drives a continued
expansion of the immune reaction, such as is seen
in persistent infection or in malignancies.
The Cytotoxic Granule-Mediated
Cell Death Pathway
The molecular characterization of several inher-
ited disorders leading to HS in the past 5 years has
144 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
revolutionized our understanding of HS. Genes

associated with inherited forms of HS are part of
the cytotoxic granule-mediated cell death pathway
and shed light on a previously unsuspected role for
this pathway in lymphocyte homeostasis.
13
The granule exocytosis cytotoxic pathway is
a rapid, powerful, and iterative mechanism adapted
to the killing of infected cells.
13,22–24
Cytotoxic T
lymphocytes (CTLs) and NK cells contain cyto-
plasmic lysosomes that can undergo regulated
secretion in response to external stimuli. These
lysosomes contain perforin (the central protein
for CTL-mediated killing), granzyme, and other
granule components. In resting CTLs, these cyto-
toxic granules move back and forth along micro-
tubules by means of kinesin- and dynein-based
motors but often cluster around the microtubule
organizing centre (MTOC) in the absence of exter-
nal stimuli (Figure 2A). Granule secretion is trig-
gered by the recognition of a target cell via the
T-cell receptor and/or other receptors yet to be iden-
tified at the plasma membrane of the CTLs and NK
cells. Within the CTL, the MTOC moves from a
perinuclear region to the contact site, repolarizing
the microtubule network toward the target cell
within minutes of target cell recognition. Granules
migrate along microtubules to the area of cell
contact in a coordinated process and fuse with

the plasma cell membrane, creating an immuno-
logic synapse (Figure 3; see also Figure 2A). Their
components are secreted into the intracellular
junction, and perforin and granzyme cooperate
to mediate apoptosis of the target cell within 5 min-
utes of receptor engagement. Not all granules are
exocytosed, and the remaining granules are ready
for new target interaction and killing. The immuno-
logic synapse is a distinct topologic re-arrangement
of cell surface proteins formed by a ring of adhe-
sion proteins (leukocyte function–associated anti-
gen 1 and talin) surrounding a central domain
containing a patch of signalling proteins and a
distinct secretory domain in which granule exo-
cytosis occurs.
The fact that all hereditary forms of HS have
defects of cytotoxic T- and NK-cell function
strongly suggests that dysfunction of this subset
of lymphocytes likely plays a key role in all forms
Figure 1 Schematic overview of antigen specific
CD8+ T-cell response in a normal individual (A) and
in a patient with hemophagocytic syndrome (B). In
response to an infectious trigger, antigen-specific CD8
+
T cells transiently undergo massive expansion, use
cell-mediated cytolysis, and produce interferon-␥ (IFN-␥).
After pathogen clearance, this immune response is
self-limiting and most cells die, leaving a reduced
number of memory T and B cells. During the course
of hemophagocytic syndrome, uncontrolled expansion

of antigen-specific effectors occurs. Activated lym-
phocytes secrete high levels of INF-␥ and induce a feed-
back loop on macrophage and T cells, which continu-
ously activate each other and expand. High levels of
inflammatory cytokines are secreted, including IFN␥,
tumour necrosis factor-␣, interleukin (IL)-1, IL-6, and
IL-18. Activated macrophages phagocytose bystander
hematopoietic cells (hemophagocytosis). Activated
lymphocytes and macrophages infiltrate various organs,
resulting in massive tissue necrosis and organ failure.
A
B
of HS, whether they are acquired or inherited.
Important, the hereditary forms clearly show us that
T cells and NK cells are the trigger for HS, and
gaining better control of T- and NK-cell activation
is the best way to manage and control the disease.
Clinical, Biologic, and Pathologic Features
The clinical presentation of HS is generally acute and
dramatic (Table 1). Typically, patients become
acutely ill with the sudden onset of a high and
unremitting fever. Splenomegaly is the second most
common clinical finding and can be associated with
hepatomegaly, lymphadenopathies, jaundice, and
CNS symptoms including confusion, seizures, and
(more rarely) focal deficits. A maculopapular skin
rash and abdominal distension have also
been described. These clinical findings are sugges-
tive of acute viral infections such
as Epstein-Barr virus (EBV) infection,

Cytomegalovirus infection, or viral hepatitis, and the
diagnosis is further complicated by the association
of these infections with HS.
25,26
Biologic alterations
include cytopenia, especially anemia and thrombo-
cytopenia. Liver dysfunction, hypertriglyceridemia,
hyponatremia, hypofibrinogenemia, and elevated
ferritin levels can also occur. Uncontrolled prolif-
eration of T cells exhibiting the activation markers
CD25 and human leukocyte antigen (HLA) class II
and activation of macrophages that phagocytose
Pediatric Hemophagocytic Syndromes — Jabado et al 145
Figure 2 Cytotoxic granules in wild-type cytotoxic T
lymphocytes (CTLs) and in CTLs from patients with
genetic defects. A, Illustrations of the distribution of
cytotoxic granules on microtubules (lines) in a resting
human CTL(left panel). Perforin and granzyme are rep-
resented as red and green circles inside granules; one
granule of each only is shown for clarity. After a CTL
encounters a target cell, cytotoxic granules polarize and
move along microtubules (middle panel) to the micro-
tubule organizing centre (in blue), which migrates to
the immunologic synapse and induces apoptosis of the
target cell after the endocytosis of cytotoxic granules
in its cytoplasm (right panel). B, Illustration of images
of CTLs from patients lacking Lyst (Chédiak-Higashi
syndrome), MUNC13-4 (FHL3), or RAB27A(Griscelli
syndrome 2) conjugated with target cells.
Figure 3 Schematic representation of cytotoxic gran-

ule exocytosis and target killing following target recog-
nition by cytotoxic T lymphocytes (CTLs) or natural
killer (NK) cells) Recognition of a peptide–major his-
tocompatibility complex class I molecule presented
by a target cell induces activation of cytotoxic lym-
phocytes (CTLs and NK cells). After cell conjugate for-
mation, activated lymphocytes polarize their lytic gran-
ules toward the cell-to-cell contact, organized as an
immunologic synapse. RAB27Ais expected to promote
the terminal transport and/or the docking step of the
cytotoxic granules at the immunologic synapse. For its
function, RAB27Apotentially associates with unknown
effectors and with MUNC13-4. MUNC13-4 functions
as a priming factor, allowing cytotoxic granules to
reach a fusion-competent state before membrane fusion
and granule secretion occur. In 30% of patients with
familial hemophagocytic lymphohistiocytosis (FHL),
cytotoxic granules are defective in their functional per-
forin content (FHL2); in another 30% of the patients,
cytotoxic granules are defective in their priming state
and thus secretion (FHL3). Defective RAB27A in
patients with Griscelli syndrome 2 impairs terminal
transport and thus exocytosis of the lytic granule con-
tents. X-linked lymphoproliferation and polymerization
of perforin are represented with a question mark because
there is no experimental proof that they act as repre-
sented in this scheme.
146 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
blood cells are a hallmark of this syndrome. Because
of their “homing” to tissues, especially those of the

reticuloendothelial system, phenotyping of circu-
lating blood lymphocytes is often inconclusive and
should not lead to the exclusion of a diagnosis of
HS. A consistent immunologic finding in active
phases of HS is impaired cytotoxic activity of NK
cells.
27,28
Activated T cells and macrophages infil-
trate multiple organs, and histopathologically, hemo-
phagocytosis is seen in bone marrow, spleen, liver,
lymph nodes, and occasionally the CNS and skin.
In the brain, the inflammatory cells form perivas-
cular foci, suggesting a blood-derived tissue infil-
tration. Activated macrophages may engulf (phago-
cytose) erythrocytes, and leukocytes, as well as
platelets, their precursors, and cellular fragments.
These cells appear to be “stuffed” with other blood
cells. In the presence of strong clinical and biologic
suspicion of HS, it is important that pathologic
analysis be repeated if results are initially negative.
Immune cell infiltration results in massive tissue
necrosis, organ failure, and death in the absence of
effective treatments.
Etiology
Based on an inheritance pattern, HS can be divided
into inherited (or primary) HS and acquired (or
reactive) HS.
Table 1
Clinical features %
Fever 80-100

Splenomegaly 55-100
Hepatomegaly 45-97
Lymphadenopathies 17-52
Rash 19-65
CNS symptoms (seizures, 19-47
confusion etc…)
Abdominal pain, distention 50
Laboratory abnormalities
Anemia 89-100
Thrombocytopenia 82-100
Neutropenia 58-87
Hypertriglyceridemia 59-100
Hypofibrinogenemia 19-85
Hyperbilirubinemia 74
DIC and increased d-dimers 20-65
Pathology findings %
Needle aspirate or biopsy of bone marrow, liver, spleen,
lymph node:
• Organ infiltration by activated T cells mostly of the CD8 lineage
(CD25 and HLA class II expression) and macrophages)
• Hemophagocytosis
• Indication of potential trigger (infection, malignancy…)
Lumbar puncture:
Pleiocytosis with activated T cells and/or macrophages
Hemophagocytosis
80-90%
Serial aspirate(s)/biopsy(ies) may be
needed to ascertain HS
~45%
May be positive even in the absence of

clinical CNS involvement
Pediatric Hemophagocytic Syndromes — Jabado et al 147
Inherited HS
Features that suggest inherited HS include occur-
rence at a young age (mostly before the age of 3
years although late onset has also been observed);
positive family history and previously affected
family members; parent consanguinity or parents
from a highly hereditary geographic region or
ethnic community; and defective NK-cell activ-
ity, even in remission phases of HS.
Familial Hemophagocytic
Lymphohistiocytosis
Familial hemophagocytic lymphohistiocytosis
(FHL) was first described by Farquhar and Claireaux
as familial erythrophagocytic lymphohistiocyto-
sis.
29
The incidence of FHL has been estimated to
be 1 in 50,000 births.
30,31
Overwhelming HS is the
distinguishing and isolated feature in this disor-
der; there are no other associated signs, unlike the
other inherited forms. Symptoms of HS are usually
evident within the first 3 months of life and can even
develop in utero. Rare cases with delayed onset have
been observed. HS most often occurs in previously
healthy young children, which suggests the need for
an exogenous trigger prior to the onset of clinical

manifestations. In susceptible children, infection
with intracellular pathogens (viral and fungal,
among others) is the most likely trigger for disease
manifestation.
32
HS in FHL is invariably lethal
unless treatment with allogeneic stem-cell trans-
plantation is performed.
33
Previously, linkage analy-
sis using homozygosity mapping in four hereditary
FHLfamilies of Pakistani descent identified a locus
(FHL1) on chromosome 9q21.3-22.
34
However, no
causative gene has been so far associated with this
locus. Association of this locus with FHL seems
restricted to Pakistani families although not all
FHLcases in Pakistani families segregate with this
locus.
35
Using genome wide linkage analysis, two
additional loci have been identified on chromo-
somes 10q21-22 (FHL2)
36
and 17q25 (FHL3),
35
and there is further evidence of additional genetic
heterogeneity and of a yet-undefined gene or genes
(G. de St Basile, unpublished data).

FHL2: Perforin Deficiency
The cytolytic effector perforin, present in cytotoxic
granules, was the first gene identified as causing
FHL.
37
As a consequence of perforin gene muta-
tions, perforin protein expression is diminished to
barely detectable in cytotoxic granules,
32,37,38
lead-
ing to defective cytotoxic activity. In normal cells,
following release from lytic granules, perforin is
thought to oligomerize in order to form a pore-like
structure in the target cell membrane, analogous
to the C9 component of complement.
22
Failure of
perforin activity is etiologically linked to the
development of FHL, and its deficiency accounts
for one-third of patients with FHL.
FHL3: Munc13-4 Deficiency
Patients whose disease is associated with FHL3
locus present typical features of FHL and are
indistinguishable from patients with a perforin
(ie, FHL2) defect. In patients with FHL3, however,
perforin is normally expressed and is functional.
FHL3 was found to be associated with mutations
in the gene UnC13D encoding for hMunc13-4, a
member of the Munc13-UNC13 family.
35

Six dif-
ferent hMunc13-4 mutations have so far been
identified in patients with FHL3 from seven dif-
ferent families. Studies of the exocytosis of cyto-
toxic granules in lymphocytes from patients with
FHL3 mutations showed that Munc13-4 is required
for the release of the lytic granule contents but not
for other secretory pathways, including the secre-
tion of IFN-␥ from T cell antigen receptor
(TCR)–activated lymphocytes.
35
Thus, hMunc13-4
is an essential effector of the cytolytic granule
pathway. Munc13-4–deficient lymphocytes can
make normal contacts with target cells, stable
conjugates, and polarize the lytic machinery as
effectively as do control lymphocytes. However,
when Munc 13-4 is lost in CTLs, cytotoxic gran-
ules dock at the membrane in the immunologic
synapse but are not released (see Figure 2B). This
supports a role for Munc 13-4 at a late step of this
pathway in exocytosis subsequent to docking.
Munc13-4 is most probably required at a priming
step of lytic granule secretion, following granule
docking and preceding plasma granule membrane
fusion.
24,39,40
Of interest, Munc13-4 is expressed
in numerous cell type, including platelets and
lungs; however, the phenotype of patients with

FHL3 is not different from that of patients with per-
forin deficiency.
148 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
Other Molecular Defects
Underlying FHL
Perforin and Munc 13-4 deficiencies account for
only two-thirds of patients with FHL. Other genes
are certainly involved and need further investi-
gation. Analyses of new hereditary families with
affected siblings that harbour no perforin or
Munc13-4 mutations are needed and should out-
line other genes that are responsible for FHL.
Chédiak-Higashi Syndrome
A Cuban pediatrician first described Chédiak-
Higashi syndrome in 1943.
41
Hematologic abnor-
malities associated with this rare disorder were sub-
sequently reported in 1952 by Chediak,
42,43
and the
presence of monstrous cytotoxic granules was
emphasized by Higashi in 1953.
44
Chédiak-Higashi
syndrome is a rare autosomal recessive disorder
(approximately 200 cases are reported in the world)
characterized by variable degrees of occulocuta-
neous albinism, easy bruising and bleeding as a
result of deficient platelet dense bodies, recurrent

infections with neutropenia and impaired neu-
trophil functions (including impaired chemotaxis
and bactericidal activity), and abnormal NK-cell
function.
44
Neurologic involvement is variable
but often includes peripheral neuropathy, and
patients with a milder expression of the disease are
frequently referred for this symptom in adult-
hood. Most patients are diagnosed during the first
decade of life. Death often occurs in the first
decade of life from infection, bleeding, or devel-
opment of HS. HS is often triggered by ongoing
intracellular infection, including infection with
herpesviruses. The hallmark of Chédiak-Higashi
syndrome is the presence of huge cytoplasmic
granules in circulating granulocytes and many
other cell types (Figure 4A; see also Figure 2B).
These granules are peroxidase positive and con-
tain lysosomal enzymes, suggesting that they are
giant lysosomes or (in the case of melanocytes)
giant melanosomes. The underlying defect in
Chédiak-Higashi syndrome remains elusive, but
the disorder can be considered as a model for
defects in vesicle formation, fusion, or trafficking.
The normal degradative functions of this com-
partment appear to be intact. The defect is appar-
ent only in cells that require secretion of their
lysosomes. This is seen in melanosomes, major his-
tocompatibility complex class II compartments,

azurophilic granules, and lytic granules, yet no dys-
function is seen in conventional secretory cells that
use secretory granules. This is consistent with a
crucial role for the Chediak protein in cells that
have cytotoxic granules. The protein defective in
Chédiak-Higashi syndrome patients and in the
beige mouse model has been identified as the 419
kD Chédiak-Higashi syndrome 1/LYST protein.
45,46
Given the length (13.5 kb) of the Chédiak-Higashi
syndrome 1 gene (CHS1), mutation screening is
a difficult task. In patients with the classic form
of Chédiak-Higashi syndrome, nonsense or
frameshift mutations leading to early truncation of
the protein have been reported. In contrast, mis-
sense mutations were identified in the few patients
Figure 4 Illustration of hemophagocytosis and the
most prominent extrahematologic features of Griscelli
and Chédiak-Higashi syndromes. A, Hemophagocyto-
sis in the bone marrow of a patient with familial hemo-
phagocytic lymphohistiocytosis; arrow indicates an
activated macrophage that has ingested several red
blood cells. B, Partial view of the head of a child with
Griscelli syndrome 2, shown to emphasize the ashen-
grey colour of hair. Electron microscopy images of a
normal hair (left panel) and a hair of a person with
Griscelli syndrome (right panel) are shown below;
arrows indicate clumps of melanin specific for this
disease. A defect in any of the proteins (myosin Va,
RAB27A, or melanophilin) leads to identical pigmen-

tary dilution in the three forms of Griscelli syndrome
and their mouse models. C, Blood smear taken from a
patient with Chédiak-Higashi syndrome. Arrows indi-
cate large granules present in all cell lineages that ori-
ent the diagnosis toward Chédiak-Higashi syndrome.
with a milder clinical course.
45–48
The exact role
of LYST is still unknown. Overexpression of
LYST in deficient fibroblasts induces the pro-
duction of unusually small lysosomes, suggesting
that LYST is involved in lysosome fission.
Recently, the domain of LYST that controls lyso-
some size has been mapped.
49
The seemingly con-
tradictory roles of increased membrane fusion (or
decreased membrane fission), leading to enlarged
lysosomes, and the inability of lysosomes to fuse
at the plasma membrane during secretion can be
explained if LYST acts to regulate membrane
fusion/fission events. This is compatible with
recent findings that LYST interacts with a soluble
N-ethylmaleimide–sensitive factor attachment
protein receptor (SNARE protein) involved in
membrane fusion.
50
At what step of the exocytic
pathway does the function of Chédiak-Higashi
syndrome/LYST in membrane fusion/fission events

operate remains to be determined and is the object
of current work by different groups. Allogeneic
stem cell transplantation remains the only cure for
children with Chédiak-Higashi syndrome. Engraft-
ment of donor cells ensures the correction of
hematologic abnormalities. However, CNS signs
associated with Chédiak-Higashi syndrome are
not treated through this procedure and increase with
the patient’s age. In a recent report, 14 patients with
Chédiak-Higashi syndrome who underwent suc-
cessful stem cell transplantation early in the course
of their disease showed progressive neurologic dys-
function with neurologic deficits or low cognitive
abilities. These neurologic problems are not linked
to transplant-related morbidity or previous infec-
tions; they are caused by the underlying molecu-
lar defect and indicate that the benefits of correcting
the hematologic and immunologic aspects of the
disease must be weighed against the limitation of
neurologic and cognitive deficits occurring later
in life despite successful transplantation.
51
Griscelli Syndrome
First described in 1978 as a syndrome associating
immunodeficiency with partial albinism, Griscelli
syndrome is an autosomal recessive heteroge-
neous disorder characterized by a pigmentary
dilution, a silvery gray sheen of the hair, and a typ-
ical pattern of uneven distribution of large pigment
granules that is easily detectable by light-micro-

scopic examination
52,53
(see Figure 4B). Sun-
exposed areas of the patients’skin are often hyper-
pigmented, and microscopic analysis of the
dermoepidermal junction will detect an accumu-
lation of mature melanosomes in melanocytes,
contrasting with the hypopigmented surrounding
keratinocytes.
52
Although this is a rare disease,
three genetic forms of the syndrome have been
defined, as follows:
1. Griscelli syndrome 1 (mutations in MYO5A,
a gene present on 15q21): pigmentary abnor-
malities associated with neurologic features,
including hypotonia and developmental
delay.
54
2. Griscelli syndrome 2 (mutations in RAB27A,
a gene adjacent to MYO5A on 15q21)
55
: the
only form associated with HS and the only one
to be further discussed in this review.
3. Griscelli syndrome 3 (mutations in
melanophilin): isolated pigmentary
abnormalities.
56
RAB27A plays an important role in

melanocytes and in cytotoxic function. Like
patients with Chédiak-Higashi syndrome, patients
with Griscelli syndrome 2 exhibit marked hypopig-
mentation, but unlike Chédiak-Higashi syndrome
patients, their lysosomes are normal in size. In
CTLs and melanocytes, RAB27Ais required at a
late stage of secretion in order to leave the micro-
tubule cytoskeleton and dock at the plasma mem-
brane.
13,24
However, the precise function of
RAB27A differs in melanocytes and CTLs. In
melanocytes, RAB27A associates with the
melanosomal membrane and recruits melanophilin,
a synaptotagmin-like protein, which in turn inter-
acts with myosin Va, an unconventional myosin
motor that moves along the actin cytoskeleton
and tethers the melanosome at the plasma mem-
brane ready for pigment delivery. In CTLs,
RAB27Adoes not interact with either melanophilin
or myosin Va, and CTLs with mutated myosin Va
or melanophilin do not have impaired cytotoxic
activity. CTLs lacking RAB27A contain cyto-
toxic granules of normal size and morphology
that appear to polarize toward the MTOC nor-
Pediatric Hemophagocytic Syndromes — Jabado et al 149
mally (see Figure 4B). However, electron
microscopy reveals that these granules remain
aligned, one behind the other, along the micro-
tubules leading to the MTOC. They are unable to

dock at the plasma membrane in RAB27A-defi-
cient CTLs, and together these observations sug-
gest that RAB27A is required for the granules to
detach from microtubules before they can dock at
the plasma membrane. One important lesson to
emerge from studies of both the Chédiak-Higashi
and Griscelli syndromes is that although key pro-
teins such as RAB27A play roles in lysosomal
secretion in many cell types, the precise compo-
sition of the secretory machinery varies from one
cell to another.
X-Linked Lymphoproliferative Syndrome
X-linked lymphoproliferative syndrome (also
called Purtilo’s disease) was first characterized by
an extreme susceptibility to EBV infection.
57
Patients with this syndrome present with three
main phenotypes: fatal infectious mononucleo-
sis, malignant B-cell lymphomas, and dysgam-
maglobulinemia. Apatient can develop more than
one phenotype, particularly after exposure to EBV.
More than 70% of patients with X-linked lym-
phoproliferative syndrome die before the age of
10 years, and all patients with this disease die by
the age of 40 years. HS in these patients is fulmi-
nant and seems to be exquisitely triggered by the
encounter of patients with EBV. X-linked lym-
phoproliferative syndrome can result from muta-
tions in the small SH2-domain-containing pro-
tein, SAP/SH2D1A/DSHP, which can associate

with several cell surface receptors of the SLAM
family of immune receptors. Recent findings indi-
cate that SAP participates in intracellular sig-
nalling in immune cells and is required for the func-
tion of SLAM as a consequence of its capacity to
promote the recruitment and activation of the Src-
related protein tyrosine kinase FynT.
58
Of inter-
esting, several studies have identified a role of SAP
in NK cell–mediated cytotoxicity through its asso-
ciation with members of the SLAM family (ie, 2B4
and NTB-A, which are both expressed on NK
cells and some CD8+ Tcells).
59,60
Several studies
show that engagement of 2B4 or NTB-Aon these
cells activates degranulation-mediated cytotoxic-
ity.
61
In contrast, when SAPis absent, these recep-
tors play an inhibitory role in cytotoxicity.
62
Thus,
cells from patients with X-linked lymphoprolif-
erative syndrome exhibit a severe cytotoxic defect
through the engagement of these receptors,
62–64
which could compromise their ability to kill EBV-
infected B cells and could favour the occurrence

of HS.
Steps in Diagnosing Primary HS
Distinguishing primary forms from secondary
forms of HS is important not only in terms of
genetic counselling for this condition but also for
determining the appropriate therapeutic interven-
tion. The occurrence of HS at a young age should
instigate the search for a genetic cause. Micro-
scopic analysis of the hair shaft is an easy and reli-
able test for diagnosing Griscelli syndrome and
Chédiak-Higashi syndrome. In both conditions,
pigmentation dilution is characteristic, but there
is larger clumping of pigment in the hair shafts of
a patient with Griscelli syndrome than in the hair
shafts of a patient with Chédiak-Higashi syn-
drome (see Figure 4B). Carriers of these syn-
dromes have normal pigmentation. The presence
of giant intracytoplasmic granules in all cells from
the hematopoietic lineage is a hallmark of Chédiak-
Higashi syndrome; this is easy to identify in a
blood smear (see Figure 4C) and rapidly ensures
diagnosis. If pigmentation dilution orients toward
Griscelli syndrome, sequencing of the RAB27A
gene allows confirmation of that diagnosis. In the
absence of HS, molecular diagnosis of Griscelli
syndrome is important for ruling out potential
RAB27Adeficiencies, which should be treated by
allogeneic stem cell transplantation. In Chédiak-
Higashi syndrome, given the length of the CHS1
gene, mutation screening is not used as a routine

test for diagnosis and genetic counselling. An
unambiguous diagnosis of this condition can be
made without need for further genetic testing,
based on the characteristic hypopigmentation of
hair shafts and the presence of intracellular giant
granules. However, for genetic counselling of
families, segregation analysis of polymorphic
markers linked to the Chédiak-Higashi syndrome
locus on chromosome 1q43.2 in the family can be
used. In nonconsanguineous families, this approach
150 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
requires the availability of a sample of deoxyri-
bonucleic acid (DNA) from both parents and from
the patient to determine the affected haplotype in
the family. When parents are related, the identifi-
cation of a shared haplotype at the Chédiak-
Higashi syndrome locus in the parents may over-
come the unavailability of a DNAsample from the
patient. When HS is not associated with hypopig-
mentation, the biggest difficulty lies in differen-
tiating between the primary (inherited) disease
(FHL) and a secondary HS disease. A positive
family history with previously affected family
members and/or consanguinity of the parents is
highly suggestive of an inherited form. The avail-
ability of biologic samples from family members
such as parents and siblings greatly helps the mol-
ecular diagnosis of genetic causes by rapid deter-
mination of the polymorphic markers segregating
with the disease locus. However, the lack of fam-

ily history is not a reliable criterion for excluding
FHL. The study of the cytotoxic activity of T lym-
phocytes
37,40
is a reliable test with which to diag-
nose the genetic forms of HS. About 30% of FHL
cases result from a perforin defect, which can be
rapidly identified by immunofluorescence analy-
sis of perforin expression in resting cytotoxic
cells. In fact, the great majority of mutations so far
identified in FHL2 dramatically affect perforin
detection. Sequencing of the perforin gene will
confirm the diagnosis of FHL. Another group of
FHLcases (about 60%) is characterized by defec-
tive T-cell cytotoxic activity but normal perforin
expression. In half of these cases, sequencing of
the MUNC13.4 gene allows identification of FHL
from Munc13-4 deficiency. In the rest, the genetic
cause is not yet characterized. Defective T-
lymphocyte cytotoxic activity is the signature of
a primary genetic cause of HS in 90% of cases. In
approximately 10% of FHLcases, however, defects
in T-cell cytotoxic activity cannot be evidenced.
In the absence of family history, these forms can-
not be clearly distinguished from secondary forms
of HS, and they remain a diagnostic challenge.
Finally, the diagnosis of X-linked lympho-
proliferative syndrome should be confirmed by
sequencing of the SAP gene and potentially by the
analysis of SAP protein expression, with the

knowledge that a significant number of patients
with the X-linked lymphoproliferative syn-
drome–like phenotype do not have mutations in
this gene but potentially do have mutations in
other yet-uncharacterized genes.
59,60
Acquired HS
Acquired HS can be as clinically, biologically,
and pathologically overwhelming as can inherited
HS. In remission phases of HS, patients with
acquired HS have normal NK-cell activity.
Rheumatoid Diseases
In the early 1980s, several reports described
patients with systemic-onset juvenile rheumatoid
arthritis (JRA) in whom a severe coagulopathy
resembling disseminated intravascular coagulation
developed.
65
Such a coagulopathy was often asso-
ciated with changes of mental status,
hepatosplenomegaly, increased serum levels of
liver enzymes, and sharp falls in blood counts
and erythrocyte sedimentation rates. In 1985, Had-
chouel and colleagues linked these symptoms to
massive proliferation of activated nonneoplastic
macrophagic histiocytes with prominent hemo-
phagocytic activity.
66
The term macrophage acti-
vation syndrome (MAS) was eventually intro-

duced in 1993 by Stephan and colleagues in a
follow-up report originating from the same cen-
tre.
5
Over the following years, several more reports
from various countries described a number of
patients with very similar symptoms. MAS, reac-
tive hemophagocytic lymphohistiocytosis (HLH),
and HS are different denominations of the same
clinical entity. Although HS has also been observed
in a small number of patients with polyarticular
JRA and in those with collagen diseases (includ-
ing lupus, vasculitis, Kawasaki disease, dermato-
myositis, and panniculitis), it is most commonly
seen in patients with the systemic form of JRA.
67–69
It is still unclear why some individuals with
these rheumatologic disorders develop MAS dur-
ing the course of their disease. Apathogen trigger
is often present, initiating HS in this setting. In a
study including seven patients with MAS,
decreased NK-cell activity was observed in all
patients, and decreased perforin expression was
found in two of the seven patients despite a nor-
Pediatric Hemophagocytic Syndromes — Jabado et al 151
152 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
mal perforin 1 gene sequence.
70
Decreased expres-
sion of SAP transcript has also been reported in

peripheral T cells of patients with JRA.
71
A tran-
sient inhibition of the cytotoxic granule pathway
may be sufficient in a setting of immune system
disturbances such as systemic JRA or other
rheumatoid disorders. In these patients, pathogens
may not be properly cleared during the first wave
of infection, thus promoting the development of
very potent immune system activation and HS. The
hypothesis that impaired cytotoxic functions and
lack of immunoregulation by NK cells result in
MAS/HS in rheumatoid disorders remains to be
proven. What is clear is that both inherited HS and
acquired HS share the same immunologic abnor-
malities in terms of macrophage and T-lymphocyte
activation and expansion and should initially be
treated similarly, as overwhelming lymphocyte
activation.
Infection-Associated HS
In 1979, HS was described in a cohort of patients
who had serologic evidence of recent viral infec-
tions, and virus-associated HS was proposed as a
distinct clinical entity.
72
Subsequently, HS has
been reported in association with a variety of
infections, and the term “reactive hemophago-
cytic syndrome” has been suggested to distin-
guish HS associated with an identifiable infectious

or noninfectious cause from its hereditary forms.
However, the reactive and hereditary forms of the
disease are difficult to distinguish; for example,
patients with familial forms of HS may have HS
after a documented infection. Case reports and case
series on the association of infections and HLH
have been summarized.
26
The most frequent patho-
logic conditions that can cause HS are infection
by viruses (including viruses of the herpes fam-
ily, human immunodeficiency virus, and aden-
ovirus), fungal infections, bacterial and mycobac-
terial infections, and parasitic infection (including
visceral leishmaniasis and toxoplasmosis).
11,73–86
Special emphasis should be given to EBV-
associated HS. With the exclusion of inherited
disorders, this form of acquired HS seems more
severe than other types of infection-associated
HS. It is a recurrent overwhelming HS, and its out-
come is often fatal despite optimal management.
The etiology of this syndrome remains poorly
understood (see below). The resolution of HS fol-
lowing treatment of the infection suggests that in
many cases, HS is secondary to the underlying
infection. A diagnosis that takes into account all
of the underlying diseases associated with HS
would be impractical, and formal guidelines for
evaluating patients with suspected infection-

associated HLH have not been established. Exten-
sive testing for underlying infecting organisms
should be guided by epidemiologic data and the
patient's medical history.
Malignant Disorders and HS
HS has been shown to be associated with malig-
nant histiocytosis.
72
In regard to malignancies,
HS is mostly encountered in patients with T-cell
malignancies, especially T-cell lymphomas.
87–89
It can be present at onset or during the course of
treatment and usually implies relapse or escape of
the leukemic clone from chemotherapeutic
agents.
90
Although T lymphocytes lack the puta-
tive EBV receptor CD21, the presence of episo-
mal EBV genome in T-cell lymphomas
25,91–93
and
T lymphocytes from patients with virus-associated
HS is has been well described.
94
EBV-positive
T-cell lymphomas appear to elaborate TNF-␣
more frequently than either EBV-positive B-cell
lymphomas or EBV-negative T-cell lym-
phomas.

25,93
Lay and colleagues induced the
expression of CD21 in T-lymphoma cell lines and
subsequently infected these cells with EBV. High
levels of TNF-␣, IFN-␥, and IL-1␣ were secreted
by these cells after EBV infection; when the lym-
phocytes were cocultured with monocytes,
enhanced phagocytosis by monocytes was
observed. The enhanced phagocytosis was elim-
inated by the addition of antibodies against TNF-␣
and IFN-␥.
25,93
Clonal expansion of EBV-infected
T lymphocytes has been demonstrated in both
EBV-associated HS and EBV-positive T-cell lym-
phoma by the presence of homogeneous viral ter-
minal repetitive sequences. EBV-infected cells
stain positive for such T-lymphocyte markers as
CD45RO and TCR-␤. Clonality of infected T
lymphocytes is further suggested by the finding of
monoclonal re-arrangements of the TCR-␤ gene
in EBV-associated HS.
95
The distinction between
the monoclonal proliferation of T lymphocytes
seen in EBV-associated HS and EBV-positive
T-cell lymphomas may describe the extremes of
a spectrum of disordered T-lymphocyte prolifer-
ation and cytokine elaboration following EBV
infection of T lymphocytes. It is unclear whether

clonal proliferation of Tlymphocytes occurs in HS
that is associated with pathogens other than EBV.
The fact that these syndromes seem more likely
to resolve with control of the underlying infection
suggests that this may not be the case.
72
Treatment of HS
HS is a severe disease that is associated with con-
siderable morbidity and mortality unless proper
management is undertaken. Early recognition of
this syndrome and immediate aggressive thera-
peutic intervention are critical and may prevent the
development of the full-blown syndrome. Immuno-
suppression-based therapeutic strategies have rev-
olutionized management and clearly outline the
central role of T cells in disease initiation and
maintenance.
Primary HS
Treatment of primary HS needs to be considered
in two steps: (1) managing current HS and poten-
tial infectious triggers and (2) preventing HS from
recurring. There are currently two major thera-
peutic options for the management of HS in hered-
itary disorders. Ahistorical line of treatment with
guidelines developed by the Histiocyte Society and
summarized in the HLH-94 treatment protocol is
available.
96
On the basis of the former suspicion
that HS might be caused by malignant histiocytes,

this group previously instated a regimen associ-
ating high-dose parenteral corticosteroids and
etoposide injections. More recently, Cyclosporin
Awas added to this regimen, along with other mod-
ifications. Etoposide is a chemotherapeutic agent
that kills histiocytes (tissue macrophages) and
was chosen accordingly. However, this drug has
been associated with secondary leukemias and
liver toxicity, as well as a dose-dependent increase
in the rate of veno-occlusive disorders following
stem cell transplantation in patients receiving this
medication. Although it is effective in treating
HS, this protocol does not fully take into consid-
eration the key role of T-cell activation in HS.
Moreover, to our group, the use of etoposide seems
unjustified as a first line of action because of its
potential side effects and its lack of a specific tar-
get, and thus we feel that its use should be restricted
to HS associated with malignancies. Data from
molecular analyses of the known causes of hered-
itary disorders associated with HS undoubtedly
show that HS is an immunologic disease and out-
line T cells as key targets for therapeutic inter-
vention. A more recent protocol that takes this
aspect into consideration offers an immunosup-
pressive regimen combining high-dose antithy-
mocyte globulins (ATGs), high-dose parenteral
methylprednisolone, and cyclosporin A.
4,33
(Thy-

mocytes are lymphocytes; ATG derived from rab-
bits is preferred to that derived from horses.) This
approach has proved repeatedly effective in obtain-
ing good-quality remissions of HS and is cur-
rently part of the guidelines of the European Soci-
ety of Immunodeficiencies, part of the European
Group for Bone and Marrow Transplantation
(EBMT).
33
Special attention should be given to
CNS involvement in HS cases. Beside high-dose
corticosteroids, the medications used have poor
CNS penetration. In the case of a positive lumbar
puncture (LP), repeated local injections of
methotrexate in doses similar to those administered
for childhood acute lymphoblastic leukemia are
needed. Even if the LP is negative, CNS prophy-
laxis should be instituted until the time of stem cell
transplantation (Table 2).
The only therapeutic means of preventing HS
from reoccurring is hematopoietic stem cell trans-
plantation (HSCT). From the moment the diagnosis
of HS is established and an inherited cause is sus-
pected, a search for the most appropriate source
of hematopoietic stem cells should be undertaken,
even if molecular investigations to characterize the
defect are ongoing. A diagnostic and therapeutic
dilemma remains for sporadic de novo (nonfa-
milial) cases of FHL that do not involve FHL2 or
FHL3 as a molecular defect in children who are

over 3 years of age and exhibit borderline NK-cell
Pediatric Hemophagocytic Syndromes — Jabado et al 153
154 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
activity. In all other cases, HSCT is mandated and
will exclusively correct hematologic abnormali-
ties. Ideally, an HLAgenotypically identical non-
affected sibling is available, and HSCT with this
donor type is successful in 85% of cases.
33,97,98
Matched unrelated T-depleted haploidentical or
cord blood transplantations have also been per-
formed with variable success and a 5-year survival
rate ranging from 55 to 75%, depending on the
series.
33,97,98
In 20% of cases, two iterative HSCTs
were required to ensure engraftment or maintain
chimerism.
33
We here also support a conditioning
regimen that does not include etoposide and com-
bines rabbit ATG with conventional
busulfan/cyclophosphamide. Tables 2 and 3 list
guidelines recommended by the EBMT Inborn
Errors Working Party for the treatment of HS as well
as for the conditioning of patients with FHL, Griscelli
syndrome 2, and Chédiak-Higashi syndrome.
Acquired HS
Rheumatoid Disorders
The treatment strategy for MAS/HS is based on

the parenteral administration of high doses of
methylprednisolone.
67
After normalization of coag-
ulation and hematologic abnormalities, a slow
taper is then performed. Frequently, MAS is resis-
tant to corticosteroids, and cases with fatal
evolutions despite the administration of massive
Table 2
Guidelines of the European Bone Marrow Transplant/European Society for Inborn Errors group
for the treatment of inherited hemophagocytic syndromes.
1- Intra-venous Methylprednisolone:
• day 1 to day 2 (48 hours) 5mg/kg/d divided in 2 doses
• day 3 to day 4 (48 hours) 3mg/kg/d divided in 2 doses
• day 4 2mg/kg /d till disease control and serum levels of ciclosporine A of ~200-300 ng/ml, then taper
to full stop previous to stem cell transplantation.
2- Rabbit anti-thymocyte globulins (ATG)
• Day1 to day 5 (5 days) 10mg/kg/d IV infusion over 6-12 hours
3- Cyclosporine A
• begin 48-72 hours after initiating ATG
• 3mg/kg/d in continuous or in 1 hour BID infusion
• aim is to have serum levels within 200-300 ng/ml
• give oral treatment whenever disease is controlled and maintain until the beginning of the conditioning
regimen for stem cell transplantation.
4- Intrathecal Methotrexate (MTX)
Doses: as per acute lymphoblastic leukemia protocols,
6mg age 0-1 year
8mg age 1-2 years
10mg age 2-3 years
12 mg age >3 years

Regimen: DO NOT EXCEED 8 IT treatments
Presence of Central Nervous system involvement on imaging or lumbar tap
2 LPs/week for 2 weeks
1 LP/week optimally up to Stem Cell Transplant
Absence of Central Nervous Involvement at diagnosis
1 LP/week optimally up to Stem Cell Transplant
doses of steroids have been described.
67
Parenteral
administration of cyclosporin A at a dosage of 2
to 8mg/kg/d has revolutionized outcomes.
4,87,99
There are anecdotal reports on the use of etopo-
side and intravenous immunoglobulins for treat-
ment of MAS; the results conflict, and we do not
suggest the use of these drugs in MAS cases.
Therapies that inhibit T-cell function may be
expected to make patients with JRA more sus-
ceptible to the development of HS in the face of
infection; on theoretical grounds, therefore, one
may recommend that such drugs be reduced tran-
siently during episodes of infection.
Infection
Ashort course of intravenous methylprednisolone
(1–2 mg/kg/d) is often sufficient in treating HS
associated with bacterial, parasitic, and fungal
infections. This treatment is given in concert with
adequate antiinfectious agents, and it must be
administered for the shortest time necessary for
correction of the most life-threatening symptoms

associated with HS because of the added immuno-
suppression in the context of severe infection.
EBV-associated HS remains a therapeutic chal-
lenge and often has a fatal outcome despite aggres-
sive management. We suggest that this form be
treated as HS associated with inherited disorders.
New antiviral drugs such as cidofovir or ribavirin
may be useful; however, the results achieved with
these drugs in the treatment of other B lympho-
proliferative disorders associated with EBV are
conflicting. Consideration should be given to the
use of IVIG in infection-associated HS, to mini-
mize the risk of immunosuppression.
Malignancies
In malignancies, a short pulse of intravenous steroids
(2 mg/kg/d) is usually administered along with
conventional chemotherapy adapted to the under-
lying disease. With the destruction of the malignant
clone, resolution of HS is often seen and no addi-
tional treatment is needed. Etoposide (100 mg/m
2
per dose) as per the HLH-94 protocol
96
can be con-
sidered in case of resistance to corticosteroids.
Supportive Care
All HS patients should be hospitalized in tertiary
care centers with an intensive care unit at hand.
Inherited disorders often have overwhelming
rapidly progressive HS; however, this can also

be encountered in cases of acquired HS. Priority
should be given to obtaining central venous line
access, instating transfusional support, and man-
aging (whenever possible) infectious triggers.
Managing hyponatremia and kidney and liver fail-
Pediatric Hemophagocytic Syndromes — Jabado et al 155
Table 3
Guidelines of the European Bone Marrow Transplant/European Society for Inborn Errors group for
conditioning regimen for hematopoietic stem cell transplant of inherited hemophagocytic syndromes.
In all cases it is strongly recommended to obtain optimal control of hemophagocytic syndrome previous
to undertaking hematopoietic stem cell transplant.
A- Genotypical identical donor
• Rabbit ATG day-14 to –10 (5 days), dose 10mg/kg/day
• Busulfan: day –10 to –7; age <6y 5mg/kg/day X 4;age>6y 4mg/kg/dayX 4
• Cyclophosphamide: day –5 to –2; 50mg/kg/day X 4
B- Matched unrelated donor/Phenotype identical related donor/HLA-nonidentical haplo or mismatched family
donor.
• Rabbit ATG day-14 to –10 (5 days), dose 10mg/kg
• Busulfan: day –10 to –7; age <6y 5mg/kg/day X 4;age>6y 4mg/kg/dayX 4
• Cyclophosphamide: day –5 to –2; 50mg/kg/day X 4
• Positive selection of CD34+ cells in Stem cell source aiming to have T cell counts <10
4
/kg
• Ciclosporine A if T cell counts above 104/kg despite positive selection of CD34+ cells
156 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
ures should be ad hoc, especially because of the
unavoidable use of nephrotoxic antiinfectious and
immunosuppressive drugs.
Conclusions
Because so many immunologic, neoplastic,

genetic, and infectious disorders may be associ-
ated with hemophagocytic syndrome, the man-
agement of this syndrome clearly calls for a mul-
tidisciplinary approach among experienced
clinicians, pathologists, and microbiologists to
define the diagnosis and the precipitating or under-
lying illnesses. Another big challenge is to char-
acterize, on a molecular level, yet-unknown genes
responsible for diseases such as familial hemo-
phagocytic lymphohistiocytosis and X-linked lym-
phoproliferative syndrome. This should also
improve the understanding of the fine regulation
of T-cell responses, an area of major therapeutic
impact.
Acknowledgement
The authors wish to acknowledge Dr. Alain Fischer,
who initiated and furthered a substantial number
of these studies.
References
1. Scott R, Robb-Smith A. Histiocytic medullary
reticulosis. Lancet 1939;2:194–8.
2. Henter JI, Elinder G, Ost A. Diagnostic guidelines
for hemophagocytic lymphohistiocytosis. The
FHL Study Group of the Histiocyte Society.
Semin Oncol 1991;18:29–33.
3. Henter JI, Elinder G. Familial hemophagocytic
lymphohistiocytosis. Clinical review based on the
findings in seven children. Acta Paediatr Scand
1991;80:269–77.
4. Mouy R, Stephan JL, Pillet P, et al. Efficacy of

cyclosporine A in the treatment of macrophage
activation syndrome in juvenile arthritis: report
of five cases. J Pediatr 1996;129:750–4.
5. Stephan JL, Zeller J, Hubert P, et al. Macrophage
activation syndrome and rheumatic disease in
childhood: a report of four new cases. Clin Exp
Rheumatol 1993;11:451–6.
6. Wong KF, Hui PK, Chan JK, et al. The acute lupus
hemophagocytic syndrome. Ann Intern Med
1991;114:387–90.
7. Kadin ME, Kamoun M, Lamberg J. Ery-
throphagocytic T gamma lymphoma: a clinico-
pathologic entity resembling malignant histio-
cytosis. N Engl J Med 1981;304:648–53.
8. Henter JI, Ehrnst A, Andersson J, Elinder G.
Familial hemophagocytic lymphohistiocytosis
and viral infections. Acta Paediatr
1993;82:369–72.
9. Browett PJ, Varcoe AR, Fraser AG, Ellis-Pegler
RB. Disseminated tuberculosis complicated by
the hemophagocytic syndrome. Aust N Z J Med
1988;18:79–80.
10. Caksen H, Akbayram S, Oner AF, et al. A case
of typhoid fever associated with hemophago-
cytic syndrome. J Emerg Med 2003;25:321–2.
11. Campo E, Condom E, Miro MJ, et al. Tubercu-
losis-associated hemophagocytic syndrome. A
systemic process. Cancer 1986;58:2640–5.
12. Matzner Y, Behar A, Beeri E, et al. Systemic
leishmaniasis mimicking malignant histiocytosis.

Cancer 1979;43:398–402.
13. de Saint Basile G, Fischer A. Defective cyto-
toxic granule-mediated cell death pathway
impairs T lymphocyte homeostasis. Curr Opin
Rheumatol 2003;15:436–45.
14. Van Parijs L, Abbas AK. Homeostasis and self-
tolerance in the immune system: turning lym-
phocytes off. Science 1998;280:243–8.
15. Zinkernagel RM. Localization dose and time of
antigens determine immune reactivity. Semin
Immunol 2000;12:163–71, 257–344.
16. Haddad E, Sulis ML, Jabado N, et al. Frequency
and severity of central nervous system lesions in
hemophagocytic lymphohistiocytosis. Blood
1997;89:794–800.
17. Henter JI, Elinder G. Cerebromeningeal
haemophagocytic lymphohistiocytosis. Lancet
1992;339:104–7.
18. Henter JI, Nennesmo I. Neuropathologic findings
and neurologic symptoms in twenty-three chil-
dren with hemophagocytic lymphohistiocytosis.
J Pediatr 1997;130:358–65.
19. Henter JI, Elinder G, Soder O, et al. Hypercy-
tokinemia in familial hemophagocytic lympho-
histiocytosis. Blood 1991;78:2918–22.
20. Takada H, Ohga S, Mizuno Y, et al. Oversecre-
tion of IL-18 in haemophagocytic lymphohisti-
ocytosis: a novel marker of disease activity. Br
J Haematol 1999;106:182–9.
21. Hasegawa D, Kojima S, Tatsumi E, et al. Ele-

vation of the serum Fas ligand in patients with
hemophagocytic syndrome and Diamond-Black-
fan anemia. Blood 1998;91:2793–9.
22. Stepp SE, Mathew PA, Bennett M, et al. Perforin:
more than just an effector molecule. Immunol
Today 2000;21:254–6.
23. de Saint Basile G, Fischer A. The role of cyto-
toxicity in lymphocyte homeostasis. Curr Opin
Immunol 2001;13:549–54.
24. Stinchcombe J, Bossi G, Griffiths GM. Linking
albinism and immunity: the secrets of secretory
lysosomes. Science 2004;305:55–9.
25. Lay JD, Tsao CJ, Chen JY, et al. Upregulation of
tumor necrosis factor-alpha gene by Epstein-
Barr virus and activation of macrophages in
Epstein-Barr virus-infected T cells in the patho-
genesis of hemophagocytic syndrome. J Clin
Invest 1997;100:1969–79.
26. Fisman DN. Hemophagocytic syndromes and
infection. Emerg Infect Dis 2000;6:601–8.
27. Schneider EM, Lorenz I, Muller-Rosenberger
M, et al. Hemophagocytic lymphohistiocytosis
is associated with deficiencies of cellular cytol-
ysis but normal expression of transcripts relevant
to killer-cell-induced apoptosis. Blood
2002;100:2891–8.
28. Egeler RM, Shapiro R, Loechelt B, Filipovich A.
Characteristic immune abnormalities in hemo-
phagocytic lymphohistiocytosis. J Pediatr Hema-
tol Oncol 1996;18:340–5.

29. Farquhar J, Claireaux A. Familial haemophago-
cytic reticulosis. Arch Dis Child 1952;27:519–25.
30. Henter JI, Elinder G, Soder O, Ost A. Incidence
in Sweden and clinical features of familial hemo-
phagocytic lymphohistiocytosis. Diagnostic
guidelines for hemophagocytic lymphohistiocy-
tosis. The FHL Study Group of the Histiocyte
Society. Acta Paediatr Scand 1991;80:428–35.
31. Dufourcq-Lagelouse R, Pastural E, Barrat FJ, et
al. Genetic basis of hemophagocytic lympho-
histiocytosis syndrome. Int J Mol Med
1999;4:127–33.
32. Feldmann J, Le Deist F, Ouachee-Chardin M, et
al. Functional consequences of perforin gene
mutations in 22 patients with familial
haemophagocytic lymphohistiocytosis. Br J
Haematol 2002;117:965–72.
33. Jabado N, de Graeff-Meeder ER, Cavazzana-
Calvo M, et al. Treatment of familial hemo-
phagocytic lymphohistiocytosis with bone mar-
row transplantation from HLA genetically
nonidentical donors. Blood 1997;90:4743–8.
34. Ohadi M, Lalloz MR, Sham P, et al. Localization
of a gene for familial hemophagocytic lympho-
histiocytosis at chromosome 9q21.3-22 by
homozygosity mapping. Am J Hum Genet
1999;64:165–71.
35. Feldmann J, Callebaut I, Raposo G, et al.
Munc13-4 is essential for cytolytic granules
fusion and is mutated in a form of familial hemo-

phagocytic lymphohistiocytosis (FHL3). Cell
2003;115:461–73.
36. Dufourcq-Lagelouse R, Jabado N, Le Deist F, et
al. Linkage of familial hemophagocytic lym-
phohistiocytosis to 10q21-22 and evidence for
heterogeneity. Am J Hum Genet 1999;64:172–9.
37. Stepp SE, Dufourcq-Lagelouse R, Le Deist F, et
al. Perforin gene defects in familial hemo-
phagocytic lymphohistiocytosis. Science
1999;286:1957–9.
38. Kogawa K, Lee SM, Villanueva J, et al. Per-
forin expression in cytotoxic lymphocytes from
patients with hemophagocytic lymphohistiocy-
tosis and their family members. Blood
2002;99:61–6.
39. Feldmann J, Le Deist F, Fischer A, de Saint
Basile G. [Munc13-4 is essential for cytolytic
granule fusion]. Med Sci (Paris) 2004;20:144–6.
40. Feldmann J, Callebaut I, Raposo G, et al.
Munc13-4 is essential for cytolytic granules
fusion and is mutated in a form of familial hemo-
phagocytic lymphohistiocytosis (FHL3). Cell
2003;115:461–73.
41. Beguez-Cesar A. Neutropenia cronica maligna
familiar con granulaciones atipicas de los leu-
cocitos. Bol Soc Cubana Pediatr 1943:900–22.
42. Chediak M, Chediak B, Fleites O, Hernandez A.
[Presentation of a case of Cooley's anemia in a
Cuban boy; first report in Cuba.]. Bol Liga Con-
tra Cancer Havana 1952;27:20–6.

43. Chediak MM. [New leukocyte anomaly of con-
stitutional and familial character.]. Rev Hematol
1952;7:362–7.
44. Higashi O. Congenital abnormity of peroxidase
granules; a case of congenital gigantism of per-
Pediatric Hemophagocytic Syndromes — Jabado et al 157
158 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
oxidase granules, preliminary report. Tohoku J
Exp Med 1953;58:246.
45. Barbosa MD, Nguyen QA, Tchernev VT, et al.
Identification of the homologous beige and
Chediak-Higashi syndrome genes. Nature
1996;382:262–5.
46. Nagle DL, Karim AM, Woolf EA, et al. Identi-
fication and mutation analysis of the complete
gene for Chediak-Higashi syndrome. Nature
Genet 1996;14:307–11.
47. Certain S, Barrat F, Pastural E, et al. Protein
truncation test of LYST reveals heterogenous
mutations in patients with Chediak-Higashi syn-
drome. Blood 2000;95:979–83.
48. Karim MA, Suzuki K, Fukai K, et al. Apparent
genotype-phenotype correlation in childhood,
adolescent, and adult Chediak-Higashi syndrome.
Am J Med Genet 2002;108:16–22.
49. Ward DM, Griffiths GM, Stinchcombe JC,
Kaplan J. Analysis of the lysosomal storage dis-
ease Chediak-Higashi syndrome. Traffic
2000;1:816–22.
50. Tchernev VT, Mansfield TA, Giot L, et al. The

Chediak-Higashi protein interacts with SNARE
complex and signal transduction proteins. Mol
Med 2002;8:56–64.
51. Tardieu M, Lacroix C, Neven B, et al. Progres-
sive neurological dysfunctions twenty years after
allogeneic bone-marrow transplantation for Che-
diak-Higashi syndrome. Blood 2005;106:40–2.
52. Griscelli C, Durandy A, Guy-Grand D, et al. A
syndrome associating partial albinism and
immunodeficiency. Am J Med 1978;65:691–702.
53. Klein C, Philippe N, Le Deist F, et al. Partial
albinism with immunodeficiency (Griscelli syn-
drome). J Pediatr 1994;125(6 Pt 1):886–95.
54. Pastural E, Barrat FJ, Dufourcq-Lagelouse R, et
al. Griscelli disease maps to chromosome 15q21
and is associated with mutations in the myosin-
Va gene. Nat Genet 1997;16:289–92.
55. Menasche G, Pastural E, Feldmann J, et al. Muta-
tions in RAB27Acause Griscelli syndrome asso-
ciated with haemophagocytic syndrome. Nat
Genet 2000;25:173–6.
56. Menasche G, Ho CH, Sanal O, et al. Griscelli syn-
drome restricted to hypopigmentation results
from a melanophilin defect (GS3) or a MYO5A
F-exon deletion (GS1). J Clin Invest
2003;112:450–6.
57. Purtilo DT, Cassel CK, Yang JP, Harper R.
X-linked recessive progressive combined variable
immunodeficiency (Duncan's disease). Lancet
1975;1:935–40.

58. Chen R, Relouzat F, Roncagalli R, et al. Mole-
cular dissection of 2B4 signaling: implications for
signal transduction by SLAM-related receptors.
Mol Cell Biol 2004;24:5144–56.
59. Engel P, Eck MJ, Terhorst C. The SAPand SLAM
families in immune responses and X-linked lym-
phoproliferative disease. Nat Rev Immunol
2003;3:813–21.
60. Chan B, Lanyi A, Song HK, et al. SAP couples
Fyn to SLAM immune receptors. Nat Cell Biol
2003;5:155–60.
61. Moretta A, Bottino C, Vitale M, et al. Activating
receptors and coreceptors involved in human
natural killer cell-mediated cytolysis. Annu Rev
Immunol 2001;19:197–223.
62. Parolini S, Bottino C, Falco M, et al. X-linked
lymphoproliferative disease. 2B4 molecules dis-
playing inhibitory rather than activating function
are responsible for the inability of natural killer
cells to kill Epstein-Barr virus-infected cells. J
Exp Med 2000;192:337–46.
63. Tangye SG, Cherwinski H, Lanier LL, Phillips
JH. 2B4-mediated activation of human natural
killer cells. Mol Immunol 2000;37:493–501.
64. Tangye SG, Phillips JH, Lanier LL, Nichols KE.
Functional requirement for SAPin 2B4-mediated
activation of human natural killer cells as revealed
by the X-linked lymphoproliferative syndrome.
J Immunol 2000;165:2932–6.
65. Silverman ED, Miller JJ 3rd, Bernstein B, Shafai

T. Consumption coagulopathy associated with
systemic juvenile rheumatoid arthritis. J Pediatr
1983;103:872–6.
66. Hadchouel M, Prieur AM, Griscelli C. Acute
hemorrhagic, hepatic, and neurologic manifes-
tations in juvenile rheumatoid arthritis: possible
relationship to drugs or infection. J Pediatr
1985;106:561–6.
67. Grom AA. Macrophage activation syndrome and
reactive hemophagocytic lymphohistiocytosis:
the same entities? Curr Opin Rheumatol
2003;15:587–90.
68. Grom AA, Villanueva J, Lee S, et al. Natural killer
cell dysfunction in patients with systemic-onset
juvenile rheumatoid arthritis and macrophage
activation syndrome. J Pediatr 2003;142:292–6.
Pediatric Hemophagocytic Syndromes — Jabado et al 159
69. Grom AA. Natural killer cell dysfunction: a com-
mon pathway in systemic-onset juvenile rheuma-
toid arthritis, macrophage activation syndrome,
and hemophagocytic lymphohistiocytosis? Arthri-
tis Rheum 2004;50:689–98.
70. Normand N, Lehamn T, Elkon K, Onel K. Lower
expression of perforin in CD8+ Tcells in patients
with systemic onset juvenile rheumatoid arthri-
tis [abstract]. Arthritis Rheum 2000;Suppl:S472.
71. Takei M, Ishiwata T, Mitamura K, et al. Decreased
expression of signaling lymphocytic-activation
molecule-associated protein (SAP) transcripts
in T cells from patients with rheumatoid arthri-

tis. Int Immunol 2001;13:559–65.
72. Risdall RJ, McKenna RW, Nesbit ME, et al.
Virus-associated hemophagocytic syndrome:
a benign histiocytic proliferation distinct
from malignant histiocytosis. Cancer
1979;44:993–1002.
73. Abdelkefi A, Ben Othman T, Torjman L, et al.
Plasmodium falciparum causing hemophago-
cytic syndrome after allogeneic blood stem cell
transplantation. Hematol J 2004;5:449–50.
74. Albrecht H, Schafer H, Stellbrink HJ, Greten H.
Epstein-Barr virus–associated hemophagocytic
syndrome. A cause of fever of unknown origin
in human immunodeficiency virus infection.
Arch Pathol Lab Med 1997;121:853–8.
75. Auerbach M, Haubenstock A, Soloman G. Sys-
temic babesiosis. Another cause of the hemo-
phagocytic syndrome. Am J Med 1986;80:301–3.
76. Babu TG, Boctor D, Davey A, et al.
Cytomegalovirus-associated hemophagocytic
syndrome in a child with Crohn disease receiv-
ing azathioprine. J Pediatr Gastroenterol Nutr
2004;39:418–21.
77. Banno S, Matsumoto Y, Sugiura Y, Ueda R.
[Human parvovirus B19 infection mimicking
systemic lupus erythematosus: case report]. Ryu-
machi 1997;37:581–6.
78. Baraldes MA, Domingo P, Gonzalez MJ, et al.
Tuberculosis-associated hemophagocytic
syndrome in patients with acquired immuno-

deficiency syndrome. Arch Intern Med
1998;158:194–5.
79. Bell MD, Wright RK. Fatal virus-associated
hemophagocytic syndrome in a young adult pro-
ducing nontraumatic splenic rupture. J Forensic
Sci 1992;37:1407–17.
80. Bird G, Peel D, McCarthy K, Williams H.
Epstein-Barr virus induced virus-associated
hemophagocytic syndrome and monoclonal TCR-
beta rearrangement: a case report. Hematol Oncol
1997;15:47–52.
81. Blanche P, Robert F, Dupouy-Camet J, Sicard D.
Toxoplasmosis-associated hemophagocytic syn-
drome in a patient with AIDS: diagnosis by the
polymerase chain reaction. Clin Infect Dis
1994;19:989–90.
82. Boruchoff SE, Woda BA, Pihan GA, et al. Par-
vovirus B19-associated hemophagocytic syn-
drome. Arch Intern Med 1990;150:897–9.
83. Cantero-Hinojosa J, Diez-Ruiz A, Santos-Perez
JL et al. Lyme disease associated with
hemophagocytic syndrome. Clin Investig
1993;71:620.
84. Chim CS, Fong CY, Ma SK, et al. Reactive
hemophagocytic syndrome associated with Peni-
cillium marneffei infection. Am J Med
1998;104:196–7.
85. Chien YH, Lee PI, Huang LM, et al. Typhoid
fever presenting as infection-associated hemo-
phagocytic syndrome: report of one case. Acta

Paediatr Taiwan 1999;40:339–40.
86. Chien CC, Chiou TJ, Lee MY, et al. Tuberculo-
sis-associated hemophagocytic syndrome in a
hemodialysis patient with protracted fever. Int J
Hematol 2004;79:334–6.
87. Real E, Gomez A, Alcaraz MJ, et al. Fulminant
hemophagocytic syndrome as presenting feature
of T-cell lymphoma and Epstein-Barr virus infec-
tion. Haematologica 2000;85:439–40.
88. Ravelli A. Macrophage activation syndrome.
Curr Opin Rheumatol 2002;14:548–52.
89. Takasaki N, Kaneko Y, Maseki N, et al. Hemo-
phagocytic syndrome complicating T-cell acute
lymphoblastic leukemia with a novel
t(11;14)(p15;q11) chromosome translocation.
Cancer 1987;59:424–8.
90. Janka G, Imashuku S, Elinder G, et al. Infection-
and malignancy-associated hemophagocytic syn-
dromes. Secondary hemophagocytic lympho-
histiocytosis. Hematol Oncol Clin North Am
1998;12:435–44.
91. Su IJ, Hsu YH, Lin MT, et al. Epstein-Barr virus-
containing T-cell lymphoma presents with hemo-
phagocytic syndrome mimicking malignant his-
tiocytosis. Cancer 1993;72:2019–27.
92. Su IJ, Wang CH, Cheng AL, Chen RL. Hemo-
phagocytic syndrome in Epstein-Barr virus-
associated T-lymphoproliferative disorders:
160 Allergy, Asthma, and Clinical Immunology / Volume 1, Number 4, Winter 2005
disease spectrum, pathogenesis, and manage-

ment. Leuk Lymphoma 1995;19:401–6.
93. Lay JD, Chuang SE, Rowe M, Su IJ. Epstein-Barr
virus latent membrane protein-1 mediates upreg-
ulation of tumor necrosis factor-alpha in EBV-
infected T cells: implications for the pathogen-
esis of hemophagocytic syndrome. J Biomed Sci
2003;10:146–55.
94. Kawaguchi H, Miyashita T, Herbst H, et al.
Epstein-Barr virus-infected T lymphocytes in
Epstein-Barr virus-associated hemophagocytic
syndrome. J Clin Invest 1993;92:1444–50.
95. Craig FE, Clare CN, Sklar JL, Banks PM. T-cell
lymphoma and the virus-associated hemo-
phagocytic syndrome. Am J Clin Pathol
1992;97:189–94.
96. Henter JI, Arico M, Egeler RM, et al. HLH-94:
a treatment protocol for hemophagocytic
lymphohistiocytosis. HLH study Group of the
Histiocyte Society. Med Pediatr Oncol
1997;28:342–7.
97. Caillat-Zucman S, Le Deist F, Haddad E, et al.
Impact of HLA matching on outcome of
hematopoietic stem cell transplantation in chil-
dren with inherited diseases: a single-center com-
parative analysis of genoidentical, haploidenti-
cal or unrelated donors. Bone Marrow Transplant
2004;33:1089–95.
98. Arico M, Janka G, Fischer A, et al. Hemo-
phagocytic lymphohistiocytosis. Report of 122
children from the International Registry. FHL

Study Group of the Histiocyte Society. Leukemia
1996;10:197–203.
99. Ravelli A, De Benedetti F, Viola S, Martini A.
Macrophage activation syndrome in systemic
juvenile rheumatoid arthritis successfully treated
with cyclosporine. J Pediatr 1996;128:275–8.